JPS6010182B2 - distribution type fuel injection pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a distributed fuel injection pump for an internal combustion engine, and more particularly to a device for reducing combustion noise when the engine is idling.

In an injection-type internal combustion engine such as a diesel engine, it is necessary to control the fuel injection amount depending on the operating state of the engine, and it is also necessary to reduce the injection rate (dQ/dt) when idling.

In other words, in the past, only the injection amount was controlled while keeping the injection rate constant, so when the engine is idling, combustion occurs in the cylinders of the engine in a short period of time due to the combustion delay caused by the decrease in the injection amount.
This resulted in an increase in combustion noise. In order to prevent this noise, an invention disclosed in Tokkoseki Publication No. 51-98426 has been proposed. In this invention, in addition to a fuel suction passage, a fuel discharge passage is provided in the fuel pressurizing chamber of the plunger head, and a solenoid valve is disposed in this discharge passage, and this solenoid valve is operated during injection at idle. A portion of the pressurized fuel is released into the chamber of the pump housing to suppress the pressure rise of the injected fuel and reduce the injection rate. However, this invention requires an expensive and highly accurate solenoid valve and an electronic circuit for controlling the solenoid valve to turn ON and OFF each time an injection is performed, which has the disadvantage of complicating the structure and increasing costs.
In view of these circumstances, the present invention has been developed to provide a distributed fuel that has a simple configuration and low cost and is capable of reducing combustion noise by lowering the injection rate during idling, thereby lowering the in-cylinder pressure at that time. The purpose is to provide injection pumps.

For this reason, the present invention provides a relief passage that opens the passage through the fuel pressure passage near the bottom dead center of the plunger, and an on-off valve that opens when the engine is idling is interposed in this relief passage. The start of the stroke of the plunger is a pre-stroke in which the plunger is not used for injection.

The embodiments shown in the drawings will be described below.

In Fig. 1, fuel is sucked and pressurized from a fuel tank by a feed pump 2, and is supplied to a chamber 41 in a pump housing 3 under the pressure regulating action of a pressure control valve 5. increases as the engine speed increases.

A plunger barrel 6 attached to the pump housing 3, particularly its distribution head 3a, is slidably equipped with a pump/distribution plunger 7, and the plunger 1 is caused to reciprocate and rotate by means not shown.

When the plunger 7 is in the suction stroke moving to the left in the figure, the fuel in the chamber chamber 4 flows from the suction passage 8 to the suction grooves 9, the number of which is equal to the number of cylinders of the engine, formed on the outer circumferential surface of the head of the plunger 7. through one of the pumping chambers 11 formed by the head of the plunger 7 and the closing plug Q.

When the plunger 7 moves to the pressure stroke (to the right in the figure), the suction passage 8 and the suction groove 9 are separated, and the fuel in the pumping chamber is compressed, and the plunger 7 moves to the right in the figure. From the fuel pressure feeding passage 12 drilled in the direction of the bag, the delivery passage 14 (
The fuel is supplied to one of the cylinders (equally distributed in the circumferential direction in a number corresponding to the number of cylinders), and is delivered to an injection nozzle (not shown) via the delivery valve 15 and injected into the cylinder. Plunger? A control sleeve turtle 6 is slidably inserted into the base on the chamber 4 side of the control sleeve 16, and a cut-off port 17 opened at a selected speed with the fuel pressure feeding passage 2 is connected to the inside of the control sleeve 16. When the fuel comes off the circumferential surface and closes into the chamber 4, the fuel flows out into the chamber 4, so the delivery to the delivery passage 14 side is stopped, and the injection ends.

Therefore, by adjusting the position of the control sleeve turtle 6, the end of the injection can be changed, that is, the injection amount can be controlled. , this lever
18, if the control sleeve 16 moves to the right in the figure, the injection amount will increase, and if it moves to the left, the injection amount will decrease. Note that the figure shows a state in which the plunger 7 is at the bottom dead center (leftmost position). As a configuration according to the present invention, a sliding hole 9 opening to the chamber 4 side is bored in the distribution head 3a, and a spring 20 is inserted into the sliding hole 1g', and a piston forming the opening/closing valve is installed. A shaped valve body 21 is slidably inserted therein, and the closed end side of the sliding hole 19 is connected to the low pressure side of the feed pump 2 or the like.

Here, the valve body 2 tatami also responds to the oil pressure in the chamber chamber 4 that changes in relation to the rotation of the engine, and when the oil pressure is low, such as at the time of starting, the spring 28' moves to the left in the figure and is activated by the snap ring 22. When the hydraulic pressure rises after starting, the spring 2 is released and moves to the right in the figure.Then, an annular groove 2 is formed on the outer peripheral surface of the plunger blue via the fuel pressure feeding passage 12 and the passage 23. This annular groove 24 forms a turtle.
A lotus passage 25 is formed in the plunger barrel 6 in correspondence with each other. Here, the annular groove 24 of the plunger 7 and one end of the lotus passage 2 that closes on the inner peripheral surface of the plunger barrel 6 match at a predetermined stroke from the bottom dead center of the plunger (hereinafter referred to as prestroke Hv). The other end of the lotus passage 25 is connected to one end of a lotus passage 26 formed in the dispensing head portion 3a.
The other end is opened on the inner peripheral surface of the sliding hole 19. Valve body 2
An annular groove 27 is formed on the outer circumferential surface of the tortoise, and the annular groove 27' is arranged to match the open end of the lotus passage 26 at a predetermined position of the valve body 21, specifically, at a position corresponding to idle rotation. There is.

And there is an annular groove 2 inside the valve body 2? A relief passage 2 fin is formed which passes through the fin and opens at the end face on the side of the chamber 4 which is a low pressure source. According to this configuration, at the time of startup, the oil pressure in the chamber 4 is extremely low, the valve body 21 is biased by the spring 20' and is moved to the left in the figure, and the open end of the lotus passage 26 is located at the left side of the valve body 21. Closed by the outer circumferential surface.

As a result, even if the annular groove 24 and the communication passage 25 match at the beginning of the stroke of the plunger 7, the fuel will not flow out and will be injected. On the other hand, at a predetermined low engine speed such as during idling, the hydraulic pressure in the chamber chamber 4 increases to some extent, so the valve body 21 moves to the right relative to the time of startup and reaches the position shown in the figure, closing the passageway 26. The end matches the annular groove 27 of the valve body 21. Therefore, even when the plunger 7 enters the fuel pumping mode, the annular groove 24 of the plunger 7 and the entrance end of the lotus passage 25 coincide with each other at the beginning of the stroke. meet, the fuel in the fuel pressure feeding passage 12 flows into the passage 2.
3. The annular groove 24, the lotus passage 25, and the lotus passage 26 flow through the annular groove 27 of the valve body 21 and from the relief passage 281 into the relatively low pressure chamber 4. Therefore, the prestroke Hv is lower than in the normal case. Fuel injection is started after a delay of a certain period of time.Furthermore, at medium and high rotation speeds, the oil pressure in the chamber chamber 4 further increases, so the valve body 21 moves to the right in the figure and again meets the open □ end of the lotus passage 26. Since the annular groove 27 of the valve body 21 is separated, the state returns to the normal state.

As described above, according to the present invention, fuel injection is performed at idle time with a delay corresponding to the prestroke Hv compared to other times.

Here, Fig. 2 shows the speed change of the plunger T. In the figure, Tv is the suction-back period (the period in which fuel is filled between the delivery passage 4 and the injection nozzle, To is the loss period, and T
H is a period corresponding to the pre-stroke, and the broken line indicates the conventional idle state (without pre-stroke), and the solid line indicates the present invention's idle state.As shown in FIG. Conventionally, there is no pre-stroke, so the plunger speed is high during the injection period To, but in the case of the present invention, due to the presence of the pre-stroke, the injection period To is brought to a region where the plunger speed is low, and therefore the injection rate decreases. .

Therefore, if you set the injection time at idle to be longer in order to maintain the same injection amount as before, the injection rate characteristic at idle as shown by the solid line in Figure 3 (the dashed line in the figure is characteristics) can be obtained, and combustion noise can be reduced by lowering the in-cylinder pressure.

Furthermore, since the injection timing is delayed, this is advantageous in terms of noise countermeasures. FIG. 4 shows another embodiment of the present invention, in which a valve body 21 constituting an on-off valve is constructed as a solenoid valve, where 30 is a solenoid and 31 is an iron core.

In this case, the spring 28' has a larger spring constant than the spring 20, and the valve body 22 does not respond to changes in the oil pressure inside the chamber 4. A microswitch 32 as a position detection switch is installed in the current supply circuit to the solenoid 30, and a passive piece 33 of this microswitch 32 is arranged opposite to a control lever 34 which is an operation input end of the governor mechanism. It is turned on at the idle position. 36 is the control lever 34
A stopper 36 regulates the idle position of the vehicle, and a stopper 36 regulates the full load position.

According to this configuration, the microswitch 32 is turned on during idle, so the solenoid 30 is energized,
The valve body 21 moves to the right as shown in the drawing as it is attracted by the iron core 31, and the open □ end of the passage 26 and the annular groove 27 of the valve body 21 match. On the other hand, at times other than idle, the micro switch 32
is off, so the solenoid 301 is not energized,
The valve body 21 moves to the left in the drawing by the spring 28' and is restricted by the snap ring 22, so that the communication passage 26 and the annular groove 27 are separated. Therefore, in this embodiment as well, it is possible to reduce the injection rate by applying a prestroke only during idle to the same machine as in the previous embodiment. As explained above, according to the present invention, by applying a prestroke only during idle, it is possible to delay the injection timing and lower the injection rate, thereby reducing combustion noise as much as possible at that time, and as a noise countermeasure. Great effect can be obtained.

A brief explanation of the box The turtle figure is a vertical sectional view of the main part showing one embodiment of the distribution type fuel injection pump according to the present invention, and Figures 2 and 3 are cross-sectional views explaining the fuel injection characteristics at idle. , FIG. 4 is a vertical sectional view of a main part showing another embodiment.

4... Chamber chamber also 6... Plunger barrel, 7... Plunger, 21... Valve body, 24... Annular groove, 25, 26... Transport passage, 27... Annular groove, 28... Relief passage, 30... Solenoid, 32 ...Micro switch, 34...Control lever.

Figure 1 Fig. Crane illustration Figure 4

Claims (1)

[Scope of Claims] 1. In a distribution type fuel injection pump that sucks in, pressure-feeds, and distributes fuel using a reciprocating and rotating plunger, the plunger communicates with a fuel pressure-feeding passage near the bottom dead center and opens the passage to a low-pressure source. In addition to providing a relief passage, this relief passage is equipped with an on-off valve that opens when the engine is idling.
A distribution type fuel injection pump characterized in that the beginning of the stroke of the plunger is a pre-stroke that does not perform injection only when idling. 2. The distribution type fuel injection pump according to claim 1, wherein the on-off valve responds to oil pressure that changes in relation to engine rotation, and is configured to open the relief passage in an idling rotation range. 3. The distribution type fuel injection pump according to claim 1, wherein the on-off valve is a solenoid valve configured to open the relief passage at the idle position in response to a signal from a position detection switch that detects the idle position of the control lever. . 4. The relief passage includes an annular groove formed on the outer circumferential surface of the plunger that slides with the plunger barrel so as to communicate with the fuel pressure passage, and an inner circumferential surface of the plunger barrel that is aligned with the annular groove near the bottom dead center of the plunger. The distribution type fuel injection pump according to any one of claims 1 to 3, further comprising a communication passage having one end opened at the radial passageway.